As many of you are aware, many of our grass species in California rice are resistant to multiple herbicides. Late watergrass aka "mimic" (Echinochloa phyllopogon), early watergrass (E. oryzoides) and barnyardgrass (E. crus-galli) are among some of our most competitive weed species, causing large yield reductions when uncontrolled.
One of the last remaining chemicals that our grass species are not yet resistant to is pendimethalin. Commercial formulations for pendimethalin registered for California rice are Prowl H2O and Harbinger. Prowl H2O is a delayed pre-emergent herbicide applied onto dry, drill-seeded fields. Harbinger is also a delayed pre-emergent herbicide, but the Harbinger system can be used in fields that are seeded by air. Both are viable uses of the chemical, and which one you choose will depend on your available equipment. For more information on how to apply, refer to the product labels.
Although I have used Prowl H2O in field trials and have a pretty good idea of its efficacy, I was curious to see how Harbinger looked in the field, since I have not yet had the opportunity to use it in a trial. I recently visited Rice Researchers, Inc., a rice breeding facility in Glenn County, where they are using a Harbinger-based program, for the second season. The photo (below) shows the rice at about 30 days after seeding. No weed species were present in the field. This is after one delayed pre-emergent Harbinger application.
It is too late to utilize pendimethalin this season, but for help incorporating pendimethalin into your herbicide plan for 2018, talk to your PCA, or give one of the UCCE Rice Advisors a call. Especially for growers that have herbicide resistant grasses, it can be a valuable tool in reducing grass populations.
- Author: Luis Espino
Moth catches have come down considerably. Looks like the worst of the infestation has passed. There are still worms out in the field; keep an eye on late planted rice.
August 9, 9:00 am-12:00 pm
New Earth Market Harvest Room
1475 Tharp Road, Yuba City
August 10, 9:00 am - 12:00 pm
3770 Hwy 45, Colusa
In the workshops, UCCE will give updates on the current weedy rice situation and research being conducted in California. Dr. Nilda Burgos, from University of Arkansas, will give a presentation on how Southern US rice producers have dealt with this weed.
There is no cost to attend but on-line registration is required. Enrollment per workshop is limited to 50 people, so please enroll early. Lunch is included.
The workshops are sponsored by the University of California Cooperative Extension and the California Rice Comission.
**CADPR and CCA CE hours are pending**
- Author: Luis Espino
We are seeing severe armyworm infestations in the field. Moth numbers have stayed relatively constant in a few locations, still on the increase in Sutter and Yolo counties. This means that egg laying may continue and we may have more worms coming up.
I have gotten several reports of pyrethroids not controlling worms. Dimilin (diflubenzuron) has been working well. However, remember that Dimilin has an 80 day pre-harvest interval. Intrepid (methoxyfenozide) received a Secion 18 today and can now be used.
The infestation is not over yet, so don't stop scouting. If you detect small worms, consider a treatment. Armyworms get their name form the fact that they move "like an army", in large numbers all at once. Worms may move from areas with severe infestations to unaffected areas of the field.
Here's a few of the pics I have received from several areas of Colusa, Glenn and Butte counties.
It may be a bit early in the season to start thinking about herbicide resistance, but in just a couple of weeks, most rice growers will have put out their last herbicide applications, and it will be time to start scouting.
University of California Cooperative Extension, in collaboration with the Agronomy Research and Information Center at UC Davis, has produced a short video which explains how to collect seed to make sure that if you do submit weed seed for testing, you get back accurate results. The form which must accompany any submitted weed seeds can be found on the UCANR Rice Website: http://rice.ucanr.edu/files/263785.pdf.